Congratulations to those of you who guessed correctly, and thank you to everyone who participated in this week’s Mystery Photo. I find patterns in nature both intriguing and beautiful — they will be the subject of more Mystery Photos! When photographing these Common Milkweed (Asclepias syriaca) seeds, I discovered that there were other creatures attracted to them besides myself – hence, today’s blog post:
LARGE MILKWEED BUGS SIPHONING MILKWEED SEEDS
Only two to four percent of Common Milkweed flowers eventually produce mature pods. Each pod contains an average of 226 seeds (all from one flower). Resembling overlapping fish scales, the seeds are arranged in a way that allows the wind to successively, from the top to the bottom of the pod, catch their silk parachutes and disperse them.
Just as milkweed pods are opening and seeds are maturing, Large Milkweed Bugs (Oncopeltus fasciatus) in all stages of metamorphosis (there are five nymphal stages, or instars) congregate on milkweed pods to feed on the seeds. (Their eggs are laid on milkweed plants.) Like all true bugs, their mouthparts (rostrum) are not adapted for biting and chewing food, but are designed for piercing and sucking. The rostrum consists of two side-by-side tubes. The milkweed bugs use one tube to pump digestive enzymes into the tough milkweed seeds and the other to siphon up the softened plant material. Like other milkweed feeders, milkweed bugs obtain poisonous compounds from the milkweed plant that are used for defense, and their orange and black coloration warns predators of their toxicity.
Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.
If you would like to order milkweed seeds, you can find several options at http://www.xerces.org/milkweed-seed-finder/
Monarch Butterflies are not the only insects whose lives are dramatically affected by the current precarious health of the Common Milkweed population. Clockwise, starting middle, top: Yellowjacket worker chewing insect to feed to larvae; White Admiral drinking nectar; Jumping Spider drinking fly innards; deceased butterfly trapped by getting proboscis caught in stigmatic slit ; Small Milkweed Bugs mating; Assassin Bug feeding on ant; Red Milkweed Beetle; Virginia Ctenucha Moth drinking nectar.
Roughly one-third of all butterfly species in North America belong to the Skipper (Hesperiidae) family. Most species possess stout bodies, wide heads and relatively small wings. An early morning walk from mid-May to mid-July through almost any field (especially one with lots of Timothy grass, which the larvae eat) will result in a flurry of tiny orange-brown wings rising into the air. It is likely that the butterflies stirred up are European Skippers (Thymelicus lineola) which roost at night on grass stalks. During the day they feed on the nectar of a variety of low-growing field flowers, including Orange Hawkweed, thistles, Ox-eye Daisy, Fleabane, White Clover, Red Clover, Selfheal, Deptford Pink, Common Milkweed, Swamp Milkweed, Dogbane and vetches. These abundant butterflies were accidentally introduced into Ontario, Canada in 1910, and their range has been expanding ever since.
Female milkweed tussock moths lay their eggs in masses on the underside of milkweed and dogbane leaves, which their larvae will eat. The hatching caterpillars are gray and hairy, but in no time they have developed the tufts of hairs that give them their name and make them resemble little mops. When still fairly young, the siblings stay together, skeletonizing the leaves they consume, leaving only the strongest veins that contain sticky latex. As they mature, the caterpillars tend to wander, and it’s unusual to find large groups of them on a single leaf. At this point they often cut through a vein in order to prevent the latex from reaching the area of the leaf where they are feeding. (Older monarch caterpillars use this same tactic.) Like monarchs, milkweed tussock moths, because they’ve consumed the cardiac glycosides contained in milkweed and dogbane leaves, are toxic to predators.
The Clymene Moth, Haploa clymene, is noted for the striking upside-down cross pattern on its forewings. Because of this design, some people refer to it as the “Crusader Moth.” A member of the Tiger Moth family (as is the Woolly Bear/Isabella Tiger Moth), the Clymene Moth can be seen flying day or night. Typically they inhabit deciduous forests and fields adjacent to them where the black, bristly larvae feed on a wide variety of plants, including willows, oaks, and members of the Aster family. In contrast to its white forewings, the Clymene Moth’s hind pair of wings is bright yellow. Its long proboscis allows it to reach deep inside the nectar-bearing hoods of Common Milkweed.